Method for producing a multielectrode lead

ABSTRACT

A wire wrapping device that includes a turntable assembly that is made up of a turntable and a driver adapted to rotate the turntable. Also, a set of payout carriers are mounted on the turntable, each payout carrier adapted to let out wire to be wrapped. A driver is adapted to turn each payout carrier relative to the turn table, the driver being user adjustable to turn each payout carrier by a selectable amount, per each complete rotation of the turntable.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.12/763,021, filed Apr. 19, 2010, pending, which was a continuation ofU.S. application Ser. No. 11/869,844, filed Oct. 10, 2007, now U.S. Pat.No. 7,698,883, which was a continuation of U.S. application Ser. No.11/285,826, filed Nov. 22, 2005, now U.S. Pat. No. 7,287,366, whichclaims the benefit of U.S. Provisional Application No. 60/630,323, filedNov. 23, 2004, the disclosure of which is incorporated herein byreference.

BACKGROUND

Bioelectrical stimulus leads in general and pain management leads inparticular have proven to be an important addition to mankind's set oftools for addressing bodily malfunction. Unfortunately, heretofore theseleads have been made one at a time in a fairly expensive operation thatincluded the use of a lathe to turn a set of insulated wires togetherabout a mandrel and then the application of heat and pressure to fusethe insulation of the wires together. Additionally, at least in partbecause the lathe wrapping process results in a lead body having avarying outer diameter and insulation thickness, the previous method hasencountered a fairly high defect rate, driving up the price forcorrectly manufactured leads. Later operations, in which electrodes arecreated in the lead body require a uniform outer diameter and insulationthickness to avoid frequent accidental damage to the lead bodies, due toan uncertain amount of insulation removal needed to reach the underlyingwire. This uncertainty has made it impractical to automate the process.

A separate problem that occurs when helically winding wires about amandrel is that of residual stress being imparted to the wires. In theprior art, two basic options are available for this kind of wirewrapping. In both options, a set of payout carriers are mounted on aturn table having a central aperture through which the core beingwrapped is advanced. The turntable is rotated about this mandrel and thepayout carriers let out wire, which helically wraps the mandrel. In afirst option, known as a planetary system, the payout carriers aremaintained in a stationary orientation relative to an absolutecoordinate system. In the second option, the payout carriers aremaintained in a stationary orientation relative to the turntable(“stationary re turntable” case). For each option, however, residualstress is imparted to wires as they are wrapped because the ideal amountof payout carrier rotation falls in between the planetary case and thestationary re turntable case.

Also, some references show a lead being made by taking a group ofinsulated wires and binding them together with an additional applicationof curable insulation. Although this is a workable method, the step ofapplying an additional coat of insulation requires some time for theinsulated wires to be dipped into the curable insulating material, andthen requires some time for that material to be cured. It would beadvantageous to find some other way of binding a set of insulated wirestogether.

BRIEF SUMMARY

In a first separate aspect, the present invention is a method ofproducing a plurality of multi-electrode leads that uses a set ofinsulated wires. These wires are continuously stranded together, therebyforming a stranded portion. Then the wires of the stranded portion arecontinuously fused together, thereby creating a fused portion.

In a second separate aspect, the present invention is a length ofworking material, more than two meters (six feet) long, comprising aflexible central mandrel and insulated wires helically wrapped about thecentral mandrel and fused together.

In a third separate aspect, the present invention is a productionfacility for producing multi-electrode leads. The facility includes awire wrapping device adapted and configured to wrap a mandrel withinsulated wires and a radiant energy application device, located so asto continuously receive the wrapped mandrel, the radiant energyapplication device being adapted to apply radiant energy to the wrappedmandrel, sufficient to fuse the insulated wires together.

In a first separate aspect, the present invention is a helically wrappedwire device wherein a set, of wires are arranged helically about a coreregion and wherein each wire defines a central axis and wherein eachwire goes through less than 0.1 rotations about its central axis forevery complete rotation about the core region.

In a second separate aspect, the present invention is a wire wrappingdevice that includes a turntable assembly that is made up of a turntableand a driver adapted to rotate the turntable. Also, a set of payoutcarriers are mounted on the turntable, each payout carrier adapted tolet out wire to be wrapped. A driver is adapted to turn each payoutcarrier relative to the turn table, the driver being user adjustable toturn each payout carrier by a selectable amount, per each completerotation of the turntable.

In a third separate aspect, the present invention is a method ofwrapping a central mandrel with flexible longitudinal elements. In themethod a set of payout carriers are revolved about the central mandrelas the central mandrel is moved along its length and the payout carrierspayout the flexible longitudinal elements, thereby helically wrappingthe mandrel with the flexible longitudinal elements. Also, the payoutcarriers are rotated a user-selected amount per rotation of theturntable.

In a first separate aspect, the present invention is a method of makinga multi-electrode probe, that starts with a length of a working materialcomprising a set of insulated wires arranged so that they are touchingalong their lengths. The working material is moved continuously in alengthwise manner through a radiant energy application zone, whereradiant energy is applied to the working material, thereby heating theworking material to soften a portion of the insulation and render itadhesive. The softened insulation is permitted to adhere together andre-cool, thereby fusing together the insulated wires.

In a second separate aspect, the present invention is a reflow assembly,comprising a radiant energy application device, adapted to create pluralradiant energy application zones, the plural radiant energy applicationzones being longitudinally and angularly displaced from each other. Inaddition, a movement assembly is adapted to move a continuous length ofworking material through the radiant energy application zones.

In a first separate aspect, the present invention is a helically wrappedwire device wherein a set of wires, insulated from one another and eachhaving a wire central axis, are arranged helically about a core regiondefining a device central axis, and wherein at each point along eachwire a radial distance may be defined between the wire central axis andthe device central axis, and wherein the radial distances, over theentirety of the device do not vary by more than 100 microns.

In a second separate aspect, the present invention is a method ofproducing a multi-electrode probe, starting with a wrapped wire workpiece having a set of wires, each surrounded by insulation which isfused together into a unitary mass and each having a most radiallyoutward surface, which is radially outward relative to the work piece,the work piece defining a work piece central axis, and wherein at eachpoint along each wire a radial distance may be defined between the workpiece central axis and the most radially outward surface of the wire.Also, at least one prospective electrode point is defined along the mostradially outward surface of each wire, each prospective electrode pointhaving an actual radial distance that is within 100 micrometers of anideal predetermined radial distance for the prospective electrode point.An energy beam is used to create an aperture through the insulation ateach prospective electrode point, the application of the energy beambeing facilitated by the actual radial distance being within 100micrometers of the ideal radial distance.

In a first separate aspect, the present invention is a wire wrap device,comprising a turntable and a set of payout carrier assemblies positionedon the turntable. Each payout carrier includes, a spool bearing wire, anelectric motor operatively connected to the spool; and an electric motorcontrol assembly adapted to control the electric motor to maintain aselected tension on the wire.

In a second separate aspect, the present invention is a method ofwrapping a central mandrel with flexible longitudinal elements. Themethod includes revolving a set of payout carriers about the centralmandrel as the central mandrel is slowly moved along its length and thepayout carriers payout the flexible longitudinal elements, therebyhelically wrapping the mandrel with the flexible longitudinal elements.In addition, each payout carrier has a spool that is turned by anelectric motor and also has a longitudinal element tension measurementdevice. The tension is regulated by controlling the electric motor inresponse to the tension measurement device.

In a first separate aspect, the present invention is a wire wrap device,comprising a turntable assembly that, in turn, includes a turntable thatdefines a central aperture, and payout carriers mounted on theturntable. In addition a payout assembly is adapted to payout flexiblemandrel and a flexible mandrel guide assembly is adapted to guide theflexible mandrel through the aperture and to maintain the flexiblemandrel in a constant rotational orientation.

In a second separate aspect, the present invention is a helicallywrapped wire work piece, comprising a mandrel and a set of insulatedwires, wrapped about the mandrel. The mandrel is not twisted anywhereover its length at a twist rate of more than one complete rotation perone meter of mandrel.

The foregoing and other objectives, features and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the preferred embodiment(s), taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a preferred manufacturing process accordingto the present invention.

FIG. 2 is a side view of a continuous work piece at a first stage in theprocess of FIG. 1.

FIG. 3 is a side view of the work piece of FIG. 2 at a later stage inthe process of FIG. 1.

FIG. 4A is a cross-sectional view of the working material of FIG. 3.

FIG. 4B is a cross-sectional view of the working material of FIG. 7.

FIG. 4C is a cross-sectional view of a working material according to analternative embodiment, including a second layer of wires.

FIG. 5 is a side view of the work piece of FIG. 3 at a first sub-stageof a further stage in the process of FIG. 1.

FIG. 6 is an illustration of an optional step in the process of FIG. 1.

FIG. 7 is a side view of an individual work piece in a further stage ofthe process of FIG. 1.

FIG. 8 is a side view of a finished product of the process of FIG. 1.

FIG. 9 is a block diagram of a wire wrap process that forms a portion ofthe process illustrated in FIG. 1.

FIG. 10 is a front view of a wire wrapping device according to thepresent invention.

FIG. 11 is a partial front of the wire wrapping device of FIG. 10,showing some features obscured from view by the front panel shown inFIG. 9.

FIG. 12 is a partial top view of the wire, wrapping device of FIG. 10,showing the payout carrier gears.

FIG. 13 is a perspective view of a portion of the wire wrapping deviceof FIG. 10, showing the payout carrier turntable.

FIG. 14 is a perspective view of a single one of the payout carriers ofthe wire wrap device of FIG. 10.

FIG. 15 is an alternative perspective view of a single one of the payoutcarriers of the wire wrap device of FIG. 10.

FIG. 16 is a block diagram of the insulation fusing portion of the leadproduction process of FIG. 1.

FIG. 17 is a perspective view of a reflow oven according to the presentinvention.

FIG. 18 is a sectional view of the reflow oven of FIG. 17 taken alongline 18-18 of FIG. 17.

FIG. 19 is an illustration of an alternative preferred embodiment of thereflow process.

DETAILED DESCRIPTION

Referring to FIGS. 1 through 8, the following text describes a preferredmethod of the present invention in schematic overview. A more detaileddiscussion of the critical steps follows.

A preferred method for practicing the present invention begins with acontinuous working material 10, which at the process beginning is only apoly tetrafluoroethylene coated stainless steel mandrel wire 12. Theworking material 10 is then helically wrapped with a set of fourinsulated wires 14 a, 14 b, 14 c and 14 d (collectively 14) at a wirewrapper 15. Each of the wires 14 includes a layer of insulation 16.While four insulated wires are used in one embodiment, those skilled inthe art will recognize that any suitable number of wires may be wrappedonto mandrel 12, using the methods of the present invention. The use offour wires in particular is not intended to be part of the invention.Referring to FIG. 4 c, in one embodiment, one or more additional layersof wires are wound in helices over the initial layer of wires 14.Typically, each additional layer of wires would be wound in the oppositedirection to the layer immediately below.

Working material 10, now comprising mandrel 12 and helically wrappedinsulated wires 14 (FIG. 4) may now be spooled and later unspooled (notshown) or fed directly to the next step in the process. In this nextstep, working material 10 may be selectively and repeatedly heated in amultistage reflow oven 18 (FIG. 1). The wires 14 are heated to atemperature that causes the insulation 16 of insulated wires 14 toapproach or achieve a phase change, thereby becoming soft and adherentand ultimately fusing together, by heating, melting and re-solidifying,in a set of angular regions 17 (FIG. 5). This process is preferablyrepeated, by feeding working material 10 through additional stages ofreflow oven 18, until the insulation 16 is fused together over itsentire angular extent.

In an alternative embodiment, the insulation of each wire 16 is chosenso that its phase transition temperature, T_(g), is different from theT_(g) of the insulation 16 of the neighboring wires 14. In particular,one or more wires 14 may have insulation 16 having a T_(g) that is highenough so that it does not undergo a phase change in the reflow oven 18,and emerges intact to lend desired physical characteristics (such asenhanced stiffness) to the working material 10. In another alternativepreferred embodiment (not shown), spacers may be used to impart desiredphysical characteristics, such as stiffness, to the overall workingmaterial 10.

At this point, the working material 10, now comprising mandrel 12 havinginsulated wires 14 at least partially fused about it, may now be spooledonto a spool 20 and stored for later work (optional step 19 in FIG. 1,shown in FIG. 6). Alternatively, step 19 is not performed and workingmaterial 10 proceeds directly to the remaining steps. Continuous workingmaterial 10 is cut (step 24) into individual lead bodies 21. Eachindividual lead body 21 may have a length of from about 10 cm (4 in) toabout 150 cm (60 in).

After the lead bodies 21 have been cut to length, mandrel 12 must beremoved from within in a mandrel removal step 28. This task may befacilitated by a coating of mandrel 12 that will ease removal, such as aPTFE coating. The mandrel removal step 28 may be a simple hand operationby a human worker.

Next, in an electrode creation step 30 a proximal aperture 38 a (FIG. 7)and a distal aperture 38 b are created through insulation 16 for eachone of wires 14. This task is performed by a laser machining station,preferably equipped with four (4) nd:YAG frequency multiplied lasers orother ultraviolet light lasers. Other removal steps may be used such asthat disclosed in U.S. Pat. No. 6,952,616 is incorporated by referenceas if fully set forth herein.

In a ring attachment step 32, a power source ring connector 40 a isattached at each proximal aperture 38 a and a tissue stimulating ringelectrode 40 b is attached at each distal aperture 38 b. This may bedone by constructing a column of conductive material and laser weldingring 40 a or 40 b to this column. One preferred method of attaching ringelectrodes is described in patent application Ser. No. 10/700,110 filedon Nov. 3, 2003, which is assigned to the same assignee as the currentapplication and is incorporated by reference as if fully set forthherein.

In one preferred embodiment mandrel 12 has an outer diameter of 330microns (13 mils) and insulated wires 14 each have a diameter of 273microns (10.75 mils), which after some compression results in anindividual lead bodies 21 having an diameter of about 711 microns (28mils).

Throughout the process as described above and in greater detail below,great care is taken to create a lead body 21 having uniform insulationthickness. It is in the creation of the apertures 38 a and 38 b throughinsulation 16 that this effort bears fruit, because it is far easier,and less prone to error, to laser machine a lead body having a uniformouter diameter (and therefore uniform laser range) then a non-uniformlead body. Particularly troubling is the case in which the range is tooclose, and too much insulation is removed, potentially ruining theentire end product.

FIGS. 9 and 10-15 describe the wire wrap process and the wire wrapper 15used for helically wrapping the mandrel or core in greater detail.Referring to FIG. 10 for a high level depiction of the wire wrapper 15,the wire wrap process begins with a mandrel payout assembly 80 and aworking material take up assembly 86 that together maintain workingmaterial 10 in well regulated motion and tension along its path.Simultaneously a controls and displays assembly 88 controls a power andlinkage assembly 82, which powers a wire payout assembly 84. Althoughone preferred embodiment permits the use of a keyboard for user input ofcontrol parameters, as indicated in FIG. 10, an alternative embodimentprovides a simple set of manual controls, such as knobs, for controlsand display assembly 82.

Assembly 84 includes a turntable 114 upon which a set of payout carriers112 are supported. Wire wrapper 15 is configured to permit a variabledegree of back twist compensation, which is implemented by rotatingcarriers 112 relative to turntable 114 at an operator specified rate. Inone embodiment an operator manipulates controls and displays assembly 88to place the right amount of back twist compensation onto wires 14. Inan alternative embodiment, the operator enters the wire and mandreldimensions and the pitch at which the wires are to be wrapped andassembly 88 computes the degree of back twist compensation necessary toprevent residual stress being placed onto wires 14.

Avoiding the placement of residual stress on wires 14 is necessary sothat this stress does not cause the wires to move spontaneously later inthe process, causing a deformation in the final shape of the lead body10, or inconsistent wire locations. After wrapping is complete, wrappedmandrel is spooled by working material take up assembly 86, whichmaintains a constant tension to avoid deforming the working material 10.In an alternative preferred embodiment, working material 10 is notspooled but progresses immediately to the next stage of processing.

In greater detail, the progress of working material 10 is maintained bythe payout assembly 80 and the take up assembly 86. The payout assembly80 includes a mandrel payout spool 100, a payout motor 102 and a dancerarm tension measurement device (not shown). Motor 102 is responsivesolely to the tension measurement, thereby maintaining constant tensionon working material 10. In take up assembly 86, working material take upspool 105 is also motor driven (not shown) and solely responsive totension measurement dancer arm 103. Take up spool 105 is movedcyclically into and out of the plane of FIG. 10, thereby causing workingmaterial 10 to spool in a repeated pattern. The tension placed onworking material 10 can be changed by changing the weighting on eitherdancer arm 103 or the payout assembly 80 dancer arm (not shown).

An additional portion of take up assembly 86 is the capstan 106, whichincludes an equal-diameter pair of wheels 108 and 110, about whichworking material 10 is looped several times. Each wheel 108 and 110bears several grooves along its exterior rim, to permit this loopingwhile preventing the working material 10 from ever rubbing againstitself. Capstan 106 is driven by an electric motor (not shown) andserves the function of stabilizing working material 10 as it exitswrapping guide plate 169 (FIG. 11).

Referring to FIG. 9, for a more complete description of the controlscheme of wrapper 15, the wire wrap pitch 92, which in practice is theratio between the capstan 106 rotation rate and the turntable 114rotation rate 96 (which equals the rotation rate of a turntable drivemotor 132 [FIG. 11]) may be set prior to beginning a wire wrapping run.Likewise the backtwist compensation ratio 96, which is the ratio of apayout carrier drive motor 134 rate [FIG. 11] to the turntable drivemotor 132 rate, may be set at the same time. Then, during a run, thespeed of the entire process may be changed by changing the turntablerotation rate command 94, which changes the capstan 106 turn rate andpayout carrier drive motor 134 rate, automatically. In other words,during operation, the capstan 106 drive and the payout carrier drivemotor 134 are slaved to the turntable drive motor 132. The rate ofcapstan 106 effectively controls the turn rate of take up spool 105(FIG. 10) and pay out spool 100 (FIG. 10) as both these spools arecontrolled to place a fixed tension on working material 10, and this canonly be accomplished if they turn at the same average rate as capstan106.

Referring to FIG. 11, power and linkage assembly 82 (FIG. 10) includesan inner shaft 122 which drives the turntable 114, and an outer shaft124 which drives the payout carriers 112, by way of a system of gears126. Inner shaft and outer shaft are driven by a first pulley 128 and asecond pulley 130, respectively. Each of these pulleys 128, 130 aredriven by a belt 129 and 131, respectively, that is in turn driven bythe turntable motor 132 and the payout carrier motor 134, respectively.

The two motors 132 and 134 are managed by the control assembly 88 (FIG.10), which regulates their relative speed within a range of relativespeeds. As noted previously, the turn rate ratio of these two motors isset before a production run is begun. In one preferred embodiment thisrange extends from equal speed (payout carriers 112 stationary relativeto the turntable 114) to the case where the outer shaft rotates at onehalf the speed of the inner shaft (payout carriers 112 stationaryrelative to an absolute frame of reference).

A number of features shown in FIGS. 11 and 13 facilitate the workings ofthe embodiment. A slip ring 140 permits electric power to be transmittedto the rotating inner assembly that includes shafts 122 and 124. On turntable 114, each payout carrier 112 includes a slip ring 142 near itsbase for supplying electricity to the payout carrier 112. Each payoutcarrier 112 includes an electric wire tension control assembly 144 thatmaintains a constant tension on the insulated wire 14 that is beingthreaded onto working material 10. Bearing assemblies 150, 152, 154 and156 facilitate the rotation of shafts 122 and 124. Plates 160 and 162support power and linkage assembly 82. A spider 164 supports a wireguide wheel 166 for each payout carrier 112, to further restrain thewires 14 as turntable 114 rotates. A first pair of pinch wheels 168 actsas an anti-rotation device for mandrel 12, to prevent it from beingtwisted by the torque imparted by wires 14, as they are being wrapped.In addition, a guide plate 169 defines an aperture that helps stabilizemandrel 12 and wires 14 at the point that the actual wrapping takesplace. Finally, a second pair of pinch wheels 171 act to furtherstabilize the mandrel 12. Together pinch wheel pairs 168 and 171 form aguide path for and prevent rotation of mandrel 12.

Referring to FIGS. 12, 14 and 15, each electric wire tension controlassembly 144 includes an electric motor 170 that drives a spool 172,both of which are mounted on a payout carrier frame 173. A wire 14follows a path defined by a dancer arm 174 which is rotatably mounted byway of an axle 175 to frame 173. Dancer arm 174 has a first dancer armguide wheel 176 and a second dancer arm guide wheel 178 about which wire14 is threaded in an “S-pattern.” Wire 14 proceeds about a frame guidewheel 180 and through a payout carrier exit guide 182. A dancer armposition measurement unit 184 monitors the position of arm 174 and sendsthis information to an electric motor controller 186. Controller 186commands the rate at which electric motor 170 turns. This arrangementpermits control of the tension in wire 14 to an accuracy of about +1%.

Referring to FIG. 12, a system of gears 126 links the motion of outershaft 124 with that of the payout carriers 112. An outer shaft gear 190,rigidly attached to outer shaft 124, causes a set of intermediate gears192 to counter rotate. Each gear 192 causes a pair of payout carriergears 194 to rotate in the same direction as gear 190. The size of gears192 is chosen simply to permit each gear 192 to mesh with two gears 194.The number of teeth of gear 192 is transparent to the turning ratios ofgears 190 and 194. Gears 194 have half the number of teeth of gear 190,so that a half counter rotation of gear 190, relative to turntable 114,causes each gear 194 to go through a complete counter rotation relativeto turntable 114. Accordingly, if the outer shaft is turning at half thespeed of the inner shaft, each payout carrier 112 undergoes a completecounter rotation per rotation of turntable 114, thereby remainingstationary relative to a fixed frame of reference. If outer shaft 124turns at the same rate as inner shaft 122, there is no relative rotationbetween any of the gears 190, 192 and 194, which causes the payoutcarriers 112 to remain stationary relative to the turn table 114.

Referring to FIG. 16, the fusing of wires 14 about mandrel 12 is shownin schematic overview. FIGS. 17-18 show a physical representation of oneembodiment of a reflow oven for accomplishing that task. The fusingprocess includes the progressive remelting of the insulation of wires 14in reflow zones 200, 201, 202 and 203 (collectively forming a reflowoven 28). Each reflow zone remelts insulation 16 over a mutuallydistinct angular portion 17 (FIG. 5) of working material 10 so thatwires 14 are held in place in the area of melted insulation, by thenearby unmelted insulation 16.

Among the critical adjustments that are made in the process is a speedadjustment 204 for the working material as it passes through the remeltzones, a working material centering adjustment 205, and an intensity anddistance adjustment 206 for each radiant energy application device. Avisual inspection system 207 aids an operator in adjusting the reflowoven 28 to achieve the best results.

FIGS. 17-19 show a stage 210 of a reflow oven assembly 28 through whichthe working material 10 is passed in order to briefly melt theinsulation about wires 14, sequentially in localized angular extents, tofuse insulated wires 14 together. Skilled persons will recognize that anadditional stage or stages could be placed after stage 210, the firstone rotated by 90.degree. Stage 210 includes two reflow zones, such aszones 200 and 201.

On either end of stage 210 is a wire guide assembly 212. Assembly 212includes a 45.degree. guide plate 214, and a wire guide micrometer stage216 that pushes on a slide block 222 that supports guide plate 214. Byturning stage 216 guide plate 214 is moved, causing the working material10 to be moved relative to stage 210. Two cartridge heater assemblies230, each including a cartridge heater 232, and a heater micrometerstage 238, for moving block 240, which supports cartridge heater 232. Bymoving stage 238 heater 232 is moved closer to or further away from asmall window 236 that permits heat to radiate to working material 10. Inone embodiment a filament heater is used in place of cartridge heater232, having a filament made of “Kanthol D” available from Duralitecorporation and having a resistance per meter for the 0.254 mm diameterwire of 26.7 ohms. A mirror 242 permits inspection of the reflow processand may be used by itself or in conjunction with a video camera (notshown).

In an alternative preferred embodiment (FIG. 19), working material 10 isfused together by a laser 250. A laser beam 252 is split and reflectedby a sequence of beam splitter/mirrors 254 to be reflected onto workingmaterial 10 at a number of places, thereby remelting the insulation 16of material 10.

The terms and expressions that have been employed in the foregoingspecification are used as terms of description and not of limitation.There is no intention, in the use of such terms and expressions, ofexcluding equivalents of the features shown and described or portionsthereof, it being recognized that the scope of the invention is definedand limited only by the claims which follow. In particular, although thecase of a four wire lead has been discussed, leads having some othernumber of insulated wires could be used, including but not limited to 8,12, 16, 24 or 36. In this application the term “continuous” does notmean “continuous in time” but rather refers to a process that may bebrought to completion without reloading the machinery involved. The term“fused” means “joined together as by melting.”

1. A method of fabricating an implantable stimulation lead fordelivering electrical pulses to tissue of a patient using, in part, awire wrapping device, the wire wrapping device comprising a plurality ofpayout carriers for letting out wire conductors to be wrapped about workmaterial, the method comprising: advancing work material to be wrappedwith the wire conductors; operating the plurality of payout carriers tolet out the wire conductors; rotating the plurality of payout carriersrelative to the work material to wrap the wire conductors about the workmaterial; providing an amount of twist to each wire conductor as thewire conductors are let out of the payout carriers to compensate fortwist caused by the wrapping of the wire conductors about the workmaterial; forming a lead body using the wrapped conductors; andfabricating a plurality terminals on the lead body, wherein theplurality of terminals are electrically connected to the conductivewires.
 2. The method of claim 1 wherein the work material comprises amandrel.
 3. The method of claim 1 wherein the work material comprisesone or more previously formed stimulation lead layers.
 4. The method ofclaim 1 wherein each of the wire conductors let out by the plurality ofpayout carriers are coated with insulative material.
 5. The method ofclaim 1 further comprising: applying heat to fuse insulative material ofthe respective wire conductors together.
 6. The method of claim 1wherein the amount of applied twist is adjustable.
 7. The method ofclaim 6 wherein the wire wrapping device comprises a display and one ormore controls to permit a user to vary the amount of applied twist. 8.The method of claim 6 wherein the amount of applied twist isautomatically adjusted in response to a selection of one or more leadcharacteristics.
 9. The method of claim 8 wherein one of the leadcharacteristics is a wire wrapping pitch.
 10. The method of claim 1wherein the amount of applied twist is controlled by controlling anamount of rotation of each of the plurality of payout carriers relativeto a rate at which the plurality of payout carriers let out theconductive wires.
 11. The method of claim 1 wherein each payout carrierof the plurality of payout carriers comprises an electric motor controlassembly, wherein the electric motor control assembly includes a dancerarm, adapted to engage the conductive wire let out by the respectivepayout carrier, the dancer arm being adapted to provide a wire tensionmeasurement, the electric motor control assembly further being adaptedto control an electric motor of the respective payout carrier in amanner responsive to said wire tension measurement.
 12. A method offabricating an implantable stimulation lead for delivering electricalpulses to tissue of a patient using, in part, a wire wrapping device,the wire wrapping device comprising a plurality of payout carriers forletting out wire conductors to be wrapped about work material, themethod comprising: advancing work material to be wrapped with the wireconductors; operating the plurality of payout carriers to rotate arespective spool of each payout carrier in a first direction to let outthe respective wire conductor and to rotate the spool in a seconddirection to impart an amount of twist to the respective wire conductoras the respective wire conductor is let out by the respective payoutcarrier; rotating the plurality of payout carriers relative to the workmaterial to wrap the wire conductors about the work material, whereinthe twist applied to each wire conductor by the plurality of payoutcarriers compensates for twist applied to the wire conductors as thewire conductors are wrapped about the work material; forming a lead bodyusing the wrapped conductors; and fabricating a plurality of terminalson the lead body, wherein the plurality of terminals are electricallycoupled to the conductive wires.
 13. The method of claim 12 wherein thework material comprises a mandrel.
 14. The method of claim 12 whereinthe work material comprises one or more previously formed stimulationlead layers.
 15. The method of claim 12 wherein each of the wireconductors let out by the plurality of payout carriers are coated withinsulative material.
 16. The method of claim 12 further comprising:applying heat to fuse insulative material of the respective wireconductors together.
 17. The method of claim 12 wherein the amount ofapplied twist is adjustable.
 18. The method of claim 17 wherein the wirewrapping device comprises a display and one or more controls to permit auser to vary the amount of applied twist.
 19. The method of claim 17wherein the amount of applied twist is automatically adjusted inresponse to a selection of one or more lead characteristics.
 20. Themethod of claim 19 wherein one of the lead characteristics is a wirewrapping pitch.
 21. The method of claim 12 wherein each payout carrierof the plurality of payout carriers comprises an electric motor controlassembly, wherein the electric motor control assembly includes a dancerarm, adapted to engage the conductive wire let out by the respectivepayout carrier, the dancer arm being adapted to provide a wire tensionmeasurement, the electric motor control assembly further being adaptedto control an electric motor of the respective payout carrier in amanner responsive to said wire tension measurement.